488 THE PALEONTOLOGY OF MINNESOTA. 



[Olassiflcatlon of paleozoic Lamelllbranchiata. 



restorations of the outline, if the figures are to be of real assistance in the identifi- 

 cation of the species, are generally not only desirable but necessary. An absolutely 

 correct reproduction of an imperfect specimen might be quite sufficient for the 

 trained specialist, but not for the beginner. He requires all we can give him, and I 

 know from experience that an approximation even to an "absolutely correct repro- 

 'duction " is anything but common among illustrations of early Lamellibranchiata. 



In the accompanying plates nearly all the specimens are represented as entire, 

 but in each instance the fact of the restoration is mentioned or indicated by a 

 fracture-like line. Respecting the drawings, I shall say only that they were in 

 every case made by myself and with as great care and fidelity to nature as I could 

 command. 



The synonomy of the species is scarcely as complete as I could wish, but as the 

 volume must be kept within certain limits, and because it is in many instances at 

 least doubtful that current identifications of the old species are really the same as 

 the originals, I have restricted the synonomy to the citation of the first work con- 

 taining a description and such of subsequent memoirs as added materially to our 

 knowledge of the objects under consideration. Desiring also to save as much space 

 as possible for general remarks, I have generally avoided what seemed unnecessary 

 repetition by giving full descriptions of the principal species only. In characterizing 

 the others I have depended chiefly upon comparisons, which, if they are complete, I 

 hold to be more useful than bare descriptions. 



While the greater part of the northwestern material used was collected by myself, and is now part 

 of my private cabinet, about one-fourth of the whole belongs to the survey museum, for which, as is shown 

 by the museum register, the specimens were collected chiefly by Prof. N. H. Winchell, Prof. C. L. Herriok, 

 and Messrs. W. H. Scofleld and Charles Schuchert. For much of the remainder I am personally indebted 

 to Mr. Scofleld, who, with unusual generosity, allowed me to select anything I desired from his extensive 

 private collection of Minnesota fossils. I am under obligations also to Dr. C. H. Robbins, of Wykoff, Min- 

 nesota, for several choice specimens from the Galena limestone of Fillmore county; likewise to Prof. C. W. 

 Hall, Mr. A. D. Meeds and Mr. A. H. Elf tman for good specimens collected by them in the vicinity of 

 Minneapolis. 



